An increasing number of standards organizations use wireless communication systems based on an orthogonal frequency division multiplexing (OFDM) technology because they can overcome inter-cell interferences. In the OFDM technology, a whole frequency band is divided into a plurality of subcarriers, and user data are mapped onto the corresponding subcarriers for transmission. The data of the communication system adopting the OFDM technology is carried by different OFDM symbols and subcarriers for transmission, and a symbol-subcarrier plane is constructed by using the OFDM symbols and the subcarriers as two-dimensional coordinates.
In establishment of specifications of long term evolution advanced (LTE-A) of a next generation radio cellular mobile communication system, in order to meet the requirement of peak rate, a carrier aggregation technology is introduced. In the carrier aggregation technology, a plurality of branch carriers are aggregated and resources of a plurality of branch carriers are scheduled for the use of a terminal simultaneously. Spectra occupied by a plurality of branch carriers may be continuous or discontinuous, the bandwidths of the branch carriers may be same or different, and each branch carrier may be a carrier compatible with an LTE terminal or a carrier only supporting an LTE-A terminal.
For a carrier which only supports LTE-A, the LTE terminal cannot perform data transmission or communication on the LTE-A carrier. In the conventional art, in order to support the characteristics of an LTE-A system, besides that a certain carrier may be configured into the one which only supports the LTE-A terminal, a part of Physical Resource Block (PRB) resource may also be configured in a branch carrier into the one which cannot be used by the LTE terminal.
Similar to other wireless communication systems, the wireless communication system based on the OFDM technology needs to transmit pilot signals, and these pilot signals are distributed on a time-frequency plane according to certain pilot patterns. In the conventional art, the specific pilot is designed on the basis of a backward compatible LTE sub-frame structure, namely, a sub-frame contains cell-specific reference signals (CRS), the first n OFDM symbols of each sub-frame are used for carrying a physical downlink control channel (PDCCH), and a physical downlink shared channel (PDSCH) for transmitting data starts from the (n+1)th OFDM symbol.
In a non-compatible carrier, because the PDCCH is not required to be transmitted, the PDSCH may start transmission from the first symbol, but the specific pilot for channel estimation is placed on the last two OFDM symbols in the first slot. A pattern of the specific pilot in a common cyclic prefix (CP) sub-frame is taken as an example, and FIG. 1-FIG. 4 show specific pilot patterns of common CP sub-frames of four different antenna ports in LTE R10 version, wherein the specific pilot appears from the 6th OFDM symbol, and PDSCH demodulation on the first 5 symbols may only be obtained by extrapolation by means of the channel estimation result on the closest 6th symbol, and thus the precision of channel estimation is affected, and the data demodulation performance is further affected.